docs: def node_stat_delta(self, char, node, *, store=True):
          """Return a dictionary describing changes to a node's stats since the
          last time you looked at it.
  
          Deleted keys have the value ``None``. If the node's been deleted, this
          returns ``None``.
  
          """
          try:
              old = self._node_stat_cache[char].get(node, {})
              new = self.node_stat_copy(self._real.character[char].node[node])
              if store:
                  self._node_stat_cache[char][node] = new
              r = dict_delta(old, new)
              return r
          except KeyError:
              return None